1. Field of the Invention
The present invention relates to a high speed power supply system that can be used to power an RF PA (Radio Frequency Power Amplifier).
2. Description of the Related Arts
In certain electronic systems, there is a need for a high-speed power supply to complement an existing DC source or low frequency power supply. As an illustrative example, a radio system may include an EER (envelope elimination and restoration) transmitter, where the RF PA is fed by a power supply which modulates the PA's power supply voltage or bias, imposing amplitude modulation onto the RF carrier signal. Typically, the power supply feeding such a PA is a linear regulator with a fast response, with the output voltage of the linear regulator controlled electronically to generate the amplitude modulation. Such a linear regulator is inefficient, as linear regulators control the output voltage via a dissipative pass transistor. A more efficient alternative could be to use a switching regulator. Often, in the case of portable battery-operated electronic devices such as mobile phones, spare switching regulators already exist within the system. However, these switching regulators lack the control bandwidth to modulate their output voltage at the rate needed to impose amplitude modulation in many modern radio systems, and therefore are not appropriate as modulators on their own.